If all of the ice in the world melted, sea levels would raise some 216 feet. But what exactly would that look like? And more specifically, what would such a worse-case scenario mean for the Earth’s population?

National Geographic has created a fascinating visual representation of this thought experiment and provided an analysis of how each continent would be affected by such a catastrophic change.

First off, this is not a blanket statement about climate change. As National Geographic notes, even scientists tracking the melting of ice around the world say it would take some 5,000 years for all the world’s ice to melt.

Still, it’s interesting to look at exactly what would happen if this scenario was taken to its most extreme conclusion.

As a result of the drastic rise in sea levels, the average temperature around the Earth would rise from 58 degrees to 80 degrees.

In North America, the entire Atlantic seaboard would vanish beneath the waves, including Florida and the Gulf Coast. Much of California would be underwater. Millions of Americans would be permanently dislocated from their homes to say nothing of the potentially insurmountable impact on natural wildlife.

And again, this scenario is only based on current population figures. Who knows what the Earth will look like in 5,000 years and how many people will be living here?

In South America, Buenos Aires, coastal Uruguay and most of Paraguay would be submerged.

Africa would technically be largely untouched but much of its would become inhabitable because of the increased temperature. In Egypt, Alexandria and Cairo would be “swamped” by flooding waters from the Mediterranean.

Many of Europe’s greatest landmarks would be destroyed: London would disappear, Venice, gone. The Netherlands and most of Denmark would also be entirely underwater.

In Asia, National Geographic says land currently inhabited by 600 million Chinese would be underwater, as would all of Bangladesh and coastal India.

The Environmental Protection Agency says that overall ice reduction will depend on several factors, including: The rate at which levels of greenhouse gas concentrations in our atmosphere continue to increase, how strongly features of the climate (e.g., temperature, precipitation, and sea level) respond to the expected increase in greenhouse gas concentrations and natural influences on climate (e.g., from volcanic activity and changes in the sun's intensity) and natural processes within the climate system (e.g., changes in ocean circulation patterns)

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"As world leaders prepare to meet in Poland for the latest United Nations summit on climate change, a major new report has warned that the chance to limit global temperature rises to below 2C is swiftly diminishing."

"Warsaw climate talks warned time is running out to close 'emissions gap':

GENEVA (Reuters) - Atmospheric volumes of greenhouse gases blamed for climate change hit a new record in 2012, the World Meteorological Organisation (WMO) said on Wednesday.

"For all these major greenhouse gases the concentrations are reaching once again record levels," WMO Secretary-General Michel Jarraud told a news conference in Geneva at which he presented the U.N. climate agency's annual Greenhouse Gas Bulletin .

Jarraud said the accelerating trend was driving climate change, making it harder to keep global warming to within 2 degrees Celsius, a target agreed at a Copenhagen summit in 2009.

"This year is worse than last year, 2011. 2011 was worse than 2010," he said. "Every passing year makes the situation somewhat more difficult to handle, it makes it more challenging to stay under this symbolic 2 degree global average."

Greenhouse gas emissions are set to be 8-12 billion tonnes higher in 2020 than the level needed to keep global warming below 2 degrees, the U.N. Environment Programme said on Tuesday.

If the world pursues its "business as usual" trajectory, it will probably hit the 2 degree mark in the middle of the century, Jarraud said, noting that this would also affect the water cycle, sea levels and extreme weather events.

"The more we wait for action, the more difficult it will be to stay under this limit and the more the impact will be for many countries, and therefore the more difficult it will be to adapt."

He said the climate system was dominated by the ocean rather than the atmosphere, and the time needed to warm the seas meant the full impact of current emissions would only be felt later.

"Even if we were able to stop today - we know it's not possible - the ocean would continue to warm and to expand and the sea level would continue to rise for hundreds of years."

Delegates from over 190 nations meet in Warsaw next week for a U.N. conference to work on emission cuts under a new climate pact to be signed by 2015, but to come into force only in 2020.

The WMO bulletin said the volume of carbon dioxide, or CO2, the primary greenhouse gas emitted by human activities, grew faster in 2012 than in the previous decade, reaching 393.1 parts per million (ppm), 41 percent above the pre-industrial level.

The amount of the gas in the atmosphere grew by 2.2 ppm, higher the average of 2.02 ppm over the past 10 years.

Carbon dioxide is very stable and is likely to remain in the atmosphere for a long time, Jarraud said. The concentrations were the highest for more than 800,000 years, he said.

"The increase in CO2 is mostly due to human activities," Jarraud said. "The actions we take now or don't take now will have consequences for a very, very long period."

The second most important greenhouse gas, methane, continued to grow at a similar rate to the last four years, reaching a global average of 1819 parts per billion (ppb) in 2012, while the other main contributor, nitrous oxide, reached 325.1 ppb.